Statistics

Author

Peh, Wee Yang.

Date of Issue

2013

School

School of Materials Science and Engineering

Related Organization

Singapore Institute of Manufacturing Technology

Abstract

Zirconia toughened alumina (ZTA) composites with addition of pristine multiwalled carbon
nanotubes (MWCNT) and nickel-coated multiwalled carbon nanotubes (Ni-MWCNT)
ranging from 0.01 wt% to 0.20 wt% were prepared using gelcasting. Samples were densified
after sintering at a temperature of 1550 °C in vacuum for 2 h and relative densities ranging
from 97% to 99% were obtained. Raman spectroscopy was conducted to confirm the
preservation of carbon nanotube structures after the completion of composite fabrication.
Agglomeration of carbon nanotubes along grain boundaries were observed under scanning
electron microscope and the agglomerate size increased with increasing carbon nanotube
content. These agglomerates were found to hinder the densification of samples and led to the
poorer mechanical performance as compared to pure ZTA. However, ZTA-Ni-MWCNT
samples were found to possess smaller pores sizes, higher sintered relative densities, smaller
carbon nanotube agglomerates as well as smaller grain sizes as compared to ZTA-MWCNT
samples. These factors were found to contribute to the slightly more superior mechanical
performance of ZTA-Ni-MWCNT samples in terms of hardness as well as flexural strength.
No significant changes in the fracture toughness of ZTA were observed when both MWCNT
and Ni-MWCNT were used.
Overall, it can be concluded that the agglomeration of carbon nanotubes was the main factor
limiting the mechanical performance of the samples. Hence, future work should be focused on
the optimization of the ratio of polyvinylpyrrolidone to carbon nanotubes in order to enhance
the dispersion of carbon nanotubes. Other factors such as types of dispersant, interfacial
interactions, surface functionalization and aspect ratio of carbon nanotubes could also be
considered for future studies.